ARM: keystone: Select TI_EDMA to be able to enable SPI driver

Select the TI EDMA to be able to enable SPI driver on Keystone
SOCs. Keystone SOCs share the EDMA IP with other TI SOCs.

Note that EDMA support hasn't been added and tested yet for
Keystone SOC data(device tree), but building it, is harmless since
driver like SPI already takes care of supporting non-dma mode
in the absence of such data.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>